Problem: $-9bcd + 10c - 4d + 3 = 3c - 5d + 7$ Solve for $b$.
Solution: Combine constant terms on the right. $-9bcd + 10c - 4d + {3} = 3c - 5d + {7}$ $-9bcd + 10c - 4d = 3c - 5d + {4}$ Combine $d$ terms on the right. $-9bcd + 10c - {4d} = 3c - {5d} + 4$ $-9bcd + 10c = 3c - {d} + 4$ Combine $c$ terms on the right. $-9bcd + {10c} = {3c} - d + 4$ $-9bcd = -{7c} - d + 4$ Isolate $b$ $-{9}b{cd} = -7c - d + 4$ $b = \dfrac{ -7c - d + 4 }{ -{9cd} }$ Swap the signs so the denominator isn't negative. $b = \dfrac{ {7}c + {1}d - {4} }{ {9cd} }$